I can say inners always take a lot longer The battery pack being out may be effecting some critical voltage Just a guess Paul WB8TSL
On Fri, Apr 26, 2013 at 5:07 PM, <engineer...@mt.net> wrote: > To all, > > I acquired a AN/URQ-10A frequency standard which appears to have received > little or no service since its birth. There are no signs of ever being > mounted in its mating rack and the unit has virtually no scratches or wear > marks on it. > > Last night I finally managed to plug it in to see how it behaved. > Obviously the D NiCads in the battery module were flat and need > replacement so I left the battery module out of the unit. As expected, the > unit powered up with all normal indications on the meter except for the > outer and inner ovens. After about three hours the indication for the > outer oven became normal but after four hours I still did not have any > indication on the inner oven reading. By that time my pillow was calling > me so I unplugged the unit to wait for further investigation fearing that > if the heater was stuck full on, internal heat damage may result (if it > hasn't already). > > But I did witness one observation that the inner oven meter indication > briefly tweaked as the power supply was shutting down telling me that the > heater element itself has continuity. This told me that the heater was > probably hot and when the power went down, the control circuitry shut the > heater drive transistor off (don't know if anyone has observed the design > of the metering circuit in this thing but the meter is connected between > the heater and the collector of the drive transistor. When cold, the > transistor is fully conducting thereby pulling this point to ground. As > the temperature reaches equilibrium, this point then become positive as the > drive transistor starts to reduce conduction. The meter then sees a > voltage at this point and indicates proper heater operation). > > Question #1: Does anyone have an idea as to how long one should wait to > see an indication of inner oven operation? Given the time it took for the > outer oven to come up, do I need more patience? > > Comment/question #2: I did download the schematics for the URQ-10 (not A > version) from the febo website but after a little disassembly and from > obvious indication of additional controls on the non-A URQ-10 schematics, > this A version is a horse of a different color. A diligent search of the > Internet has produced no results of information on the A version except for > one original NAVSHIPS OP/SVC manual for it that went on eBay a little while > ago (drats!). > > Comment/question #3: Not investing any additional time last night (sleep > required), I simply tapped on the FE-10 oscillator module enclosure and > found it to be as solid as a rock. I don't have time to do more peeking at > present but assume that this is due to (what I believe) is a Dewar > enclosure that is contained inside. Correct? If the inner oven has > cratered, is the internal oven control circuitry contained in this > enclosure accessible by any means or is it sealed forever? > > This unit may be old but it is certainly near collector status with > regards to its physical condition. > > Any help, especially schematics, would be appreciated. > > Regards, > > Greg Muir > > > > ------------------------------**------------------------------**---- > This message was sent using IMP, the Internet Messaging Program. > > > ______________________________**_________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.